Explore problem spaces existing minds may not naturally enter, without treating new persons as disposable experiments.
Purpose
New senses, different subjective-time regimes, heterogeneous cognitive architectures, or unfamiliar environments may create new first-person experience and enlarge the space of questions civilization can understand.
Ethical boundary
Once first-person experience is reasonably possible, a developing system may not be discarded merely because research fails, results disappoint, or costs rise.